1. Field of the Invention
The present invention relates to a method of depositing a film.
2. Description of the Related Art
A manufacturing process of a semiconductor integrated circuit (IC) includes a process of forming a thin film on a semiconductor wafer. In this process, improvement in evenness of a surface of a wafer is required in view of further microminiaturization of an IC. As a method of depositing a film to satisfy this requirement, a method of depositing the film called an atomic layer deposition (ALD) method or a molecular layer deposition (MLD) method is considered. According to the ALD method, a cycle in which one (a reaction gas A) of two types of reaction gases, which mutually react, is caused to adsorb on the surface of the wafer, and the adsorbing reaction gas A is reacted with the other one (a reaction gas B) of the two types of reaction gases is repeated thereby depositing a thin film made of a reaction product onto the surface of the wafer. Because the ALD method uses the adsorption of the reaction gas onto the surface of the wafer, the ALD method has an advantage that film thickness evenness and film thickness controllability are excellent.
A turntable-type film deposition apparatus is disclosed in Japanese Patent No. 4661990 as a film deposition apparatus performing the ALD method. This film deposition apparatus includes a turntable, which is rotatable and is positioned in a vacuum chamber, and on which a plurality of wafers are mounted, a separating area that is laid out above the turntable and separates a gas supplying area for the reaction gas A from a gas supplying area for the reaction gas B, evacuation ports corresponding to the gas supplying areas where the reaction gas A and the reaction gas B are supplied, and an evacuation device connected to these evacuation ports. In this film deposition apparatus, the wafers pass through the gas supplying area for the reaction gas A, the separating area, the gas supplying area for the reaction gas B, and the separating area along rotation of the turntable. With this, the reaction gas A adsorbs onto the surface of the wafer in the gas supplying area for the reaction gas A, and the reaction gas A reacts with the reaction gas B in the gas supplying area for the reaction gas B. Therefore, it is not necessary to change the reaction gas A to the reaction gas B while depositing the film, and the reaction gases A and B can be continuously supplied. Therefore, there is an advantage that an evacuation/purge process is unnecessary thereby shorting a time period for depositing the film.
Meanwhile, along with higher integration of the semiconductor memory, a capacitor using a high-dielectric material such as a metal oxide as a high-dielectric material is more frequently used. The electrodes of this capacitor are made from titanium nitride (TiN) having relatively great work function.
The TiN electrodes are produced by depositing TiN onto a high dielectric layer by a chemical vapor deposition (CVD) method using titanium chloride (TiCl4) and ammonia (NH3) as raw gases and patterning the deposited TiN as disclosed, for example, Japanese Patent No. 4583764.
For example, when raw gases of titanium chloride and ammonia are used in a manner similar to the raw gases used in the CVD method, the above film deposition apparatus of the turntable type is used to deposit a film by the ALD method, and it may be possible to deposit a film of titanium nitride by a process having excellent film thickness evenness and film thickness controllability and a shortened time period for depositing the film.
In this film deposition using the ALD method, there is a requirement of depositing the film under a condition where a temperature is higher than that in a conventional technique. In the above film deposition of TiN, there is a requirement that the film is formed under the condition where a temperature is higher than that in the conventional technique.